Selenium cell without inertia



oct. 5, 1926. 1,602,070

G. DRAGON ETTl SELENIUM CELL WITHOUT INERTIA Filed Jan. s1.' i924 Patented Oct. 5, 192.6.v

UNITED STATES GIOITANNI DRAGONETTI, OF ROME, ITALY.

SELENIUM CELL WITHOUT INERTIA.

Application filed January 31, 1924, Serial No. 689,763, and in Italy February 12, 1923.

My invention relates to improvements in selenium cells adapted to be used in many contrirances in which are made applicable their peculiar photoelectric properties. that is, the varying resistance which is produced in the selenium through the variation et the. intensity of the light by which it is struck. In a peculiar physical state, selenium when in the darkness has a Very considerable resistance, but said resistance greatly diminishes upon the selenium being exposed to the action of light.

However, whilst the variation in the con ductivity of selenium, i. e., as the resistance is reduced, lis produced nearly instruit-aneously upon thel selenium being struck by the light., the variation in the opposite sense, that is in the sense of the increase o't' the rcsfstance, upon the action of light being stopped, is delayed a certain time. This delay has been named the hysteresis or also the inertia7 ofthe selenium.

Now since in many cases' a. Very rapid variation in the resistance of the selenium would be required, the possibility of using selenium is necessarily limited because it the periods of time between two successive illuniinations are not greater than the period ol time required to reestablish the primitive resistance, the effect of the selenium cell is damped and the cell, upon a certain 'frequency of alternations being exceeded, will not work at all.

The. object of the present invention is to eliminate said drawback by l'such arrangements as to produce the variations ot tne resistance of the selenium cell with the same speed upon the diminution as well as the increase of resistance. This result I obtain by inserting a condenser between one pole of the battery feeding the cell and that end of the wire of the cell which is connected to the other pole of the battery.

Such an arrangement is shown in the annexed drawing, in which -a represents a battery ot' primary cells,v or a storage bat tery, feeding the circuit; ZJ- is the apparatus in which is utilized the Variability ot the current produced` and one side of which isconnected to one of the poles of the battery while its other side, at c1, is connected to the end of one. of the wires d, forming the winding of the selenium cell. The end c: of the other wire. (Z2 is connected to the other pole ot the battery. However from the point Q ot' the wire connecting,r the end c2 with the battery, branches off a wire which is ending at one of the plates of a condenser f], the other plate ot which is connected to the free end 7c, of the wire d1.

The arrangement may also be such that the apparatus o is inserted between the pointsl c, and c2 while 'the condenser -g--, is inz-erted between the points c, and 7a2. The apparatus -bis thus always located between one ot the poles of' the battery and the. end ot one ot the wires of the selenium cell, while the. condenser is located between the other end ot the saine wire and the other pole ot the battery.

lVith such an arrangement both the increase and the decrease of resistance are produced instantaneously, so that the fre queney ot the variations may be increased at will without thus diminishing the eiliciency of the cell.

I claim as my invention:

In combination with a selenium cell of the kind herein described, having its windingr formed of two parallel wires and one end of each wire connected to one of the poles'ot the source oi current feeding theI cell, an arrangement to produce with the .zame speed the variations` ot' the resistance ot' said cell upon a diminution as well as upon an increase of the intensity of light. Said arrangement comprising a (.ondenser inserted between the Jfree end of one of said wires and that pole of the source ot current. which is connected to the end of the other wire. l

In testimony whereof I affix my signature this 14th day of January 1924.

GIOVANNI DRAGONETTI. 

